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Forgotten Dinosaurs of the Lost Continent Part 2

Last time I gave a little background info on what I call the “Forgotten Dinosaurs of the ‘Lost Continent’”. This time we’ll look at the dinosaurs themselves.

But first I don’t feel like I was clear enough in my reasoning in the last post. Why have I bestowed these animals with the title of “forgotten”? Well even though the West Coast is a crappy place for dinosaur hunters, a few fossils beyond fragments have been found. I call them the “forgotten dinosaurs” because in discussions of Laramidia and dinosaur provincialism, they are almost never mentioned. So now I present you with the few, the proud: the dinosaurs of western Laramidia!

Aletopelta

Not too much to say here since I have already done a post about it. Nonetheless Aletopelta is unique in that it is the only genus endemic to western Laramidia (at least so far). All the other dinosaurs are known from elsewhere, whereas Aletopelta is a beast all its own.

Lambeosaurus laticaudus

Like most other dinosaurs in this discussion, Lambeosaurus laticaudus is known from the El Gallo formation of Baja California. Also, this dinosaur is a member of a genus known from elsewhere. But this dinosaur really stands out from its kin to the northeast. For one, it’s huge, possibly the largest hadrosaur known; it has been estimated at 50 feet long and over 20 tons in weight. It also had a narrow tail, which the original describers interpreted as an adaptation to swimming. The disassociated remains of several individuals have been found, including juveniles, which suggests Baja may have been a breeding ground. A couple hadrosaur specimens have been found in San Diego County, but they are too fragmented to be assignable to any genus.

A fleshed out model of Lambeosaurus at the San Diego Natural History Museum

While most of the Baja fossils have been referred to Lambeosaurus (indeed its own species of Lambeosaurus), there has been some doubt as to its exact identity. Some have suggested it might be a species of Hypacrosaurus. More recently, some think it may belong to Velafrons, a new hadrosaur known from eastern Mexico. However, without a crest, it may be difficult to determine just who Lambeosaurus laticaudus really was.

Saurolophus

It is well known that Saurolophus has been found from Canada and Asia. What people don’t know is that it has been found on the west coast as well. Way back yonder Chester Stock, one of the giants of California paleontology, discovered two skeletons of Saurolophus in the Panoche Hills of Fresno County. One, while fairly complete, was poorly preserved. The other was nearly complete and in good condition. While both lack the diagnostic crest and can’t be assigned to a specific species, they are the most complete dinosaurs found in either Alta or Baja California (or west of the Rockies for that matter)! The LA Museum plans to have a display about California dinosaurs in their new dinosaur hall. Looking at concept renderings it looks like one of these Saurolophus skeletons will make an appearance as well as what looks like a silhouette of Lambeosaurus laticaudus.

skeleton of Saurolophus, the most complete dinosaur on the West Coast

Albertosaurus

A smaller earlier relative of Tyrannosaurus, Albertosaurus is known definitively from Alberta and Montana. It may also be known from Alaska, Texas, and Baja California. Some teeth thought to belong to albertosaurus have been found in the El Gallo formation. Whether it truly is Albertosaurus or something else all together is unknown. Unlike mammals, dinosaur teeth are not very diagnostic beyond the family level. So while Albertosaurus may have lived in California, we cannot say for sure.

Cast teeth of Albertosaurus from Baja California at the San Diego Natural History Museum

Sauronitholestes

Again inferred from a couple of teeth in the Ell Gallo formation. Sauronitholestes was a dromeosaur about six feet long.

Troodon

Inferred from a tooth and a toe bone from the El Gallo formation, Troodon is famous for its relatively large brain.

Cast toe bone of Troodon at the San Diego Natural History Museum

Other dinosaurs

An ornithomimid is known from the El Gallo as well as well as several indeterminate theropod teeth. Fragments of hadrosaurs are known from many places in California such as Orange and Tehama Counties. So far no ceratopsians are known from either Alta or Baja California. This is very interesting since ceratopsians show a high degree of provincialism in eastern Laramidia Perhaps the environment in western Laramidia wasn’t suitable for ceratopsians. Or maybe we just haven’t found them yet.

I mentioned in my last post that the dinosaurs found in Alta and Baja California might throw a monkey wrench into the idea of dinosaur provincialism. Why? Well the idea stipulates that various dinosaur species are unique to their respective regions. Indeed this seems to hold true for the east of Laramidia. Pentaceratops is known only from New Mexico, Kosmoceratops is only known from Utah, and Chasmosaurus is only known from Alberta. The same goes for many other dinosaurs. But the dinosaurs of western Laramidia all seem to be dinosaurs found in Canada. According to dinosaur provincialism, they ought to be their own assemblage, because dinosaurs of the south haven’t been found in the north. See the problem? However, they may not be alone in this problem. Gryposaurus is known from Alberta but also from Utah. But maybe this isn’t such a problem since they are different species. But this still doesn’t wholly explain the dinosaurs of western Laramidia. How did genera found in the northeast somehow end up in the southwest when most other dinosaurs in the south consist of their own genera? Were they somehow able to circumvent the mountains from the north and settle into the west? Unfortunately, most of these apparently lost dinosaurs (save for Saurolophus) are represented by scrappy material. As noted Albertosaurus is inferred from just teeth! Those teeth could have belonged to an unknown theropod for all we know. While California has yielded few informative specimens, Baja California remains our best bet for finding the dinosaurs of Western Laramidia.

Who knows what we may find in the El Gallo formation. It certainly shows promise. But what I have been able to read has not been encouraging. Apparently the terrain is very uneven and the climate harsh, making it difficult to look for fossils and even harder to extract them. Also, apparently Mexico doesn’t like outsiders snooping around. According to a book on California dinosaurs, the LA Museum was pressured to cough up many of its specimens from the El Gallo and return them to Mexico. Whether this holds true for today is unknown to me but if it does it must only be for dinosaur fossils since the LA museum still has tons of Pleistocene fossils from Mexico, which they continue to find. I’d love to try and search for the dinosaurs that called Baja California (and from extrapolation maybe Alta California as well) but right now it doesn’t look like it’s in the cards. Certainly more fossils would help solve the many questions we have about dinosaur provincialism. However, the threat of stirring political ire is a little too daunting for me.

soory hit “enter too soon”. Labocania seemed to be a loner; i couldn’t find any info on any other dinosaurs from the La Bocana Roja formation. This discussion always involves talk of faunal assemblages. So being the odd man out, Labocania just didn’t make it in.